Speed control of induction motors



Dec. 11, 1928. 1,694,985

H. K. SCHRAGE SPEED CONTROL OF INDUCTION MOTORS Original Filed April 8, 1925 Inventor: Hidde K. Schrage b W y His Attogey' Patented Dec. 11, 1928.

PATENT OFFICE.

HIDDE K. SCHRAGE, OF PARIS, FRANCE, ASSIGNOR TO GENERAL ELECTRIC CO]!!- PANY, A CORPORATION OF NEW YORK.

SPEED, CONTROL. OF

Original application filed April 8, 1925, Serial No.

INDUCTION MOTORS.

21,662, and in France June 20, 1924; Divided and this application filed Sept-amber 9, 1927. Serial No. 218,546.

This application is a division of my application Serial No. 21,662, filed April 8, 1925.

My invention relates to systems wherein the speed of an induction motor is controlled ,loy variation in the magnitude of a regulatin voltage applied to its secondary circuit 'eit er through a regulating winding forming a part of the motor, or through a regulating machine interconnected with the motor, and has for its object the provision of an improved arrangement for controlling the commutation of the regulating machine or winding in a manner to render possible the utilization of regulating voltages higher than those heretofore used for this purpose.

It is well known that the speed of an induo tion motor canbe regulated by means of a variable voltage applied to its secondary circuit, and that the limit to which the regulating voltage can be increased is dependent on the commutation characteristics of the regulating winding or machine through which this voltage is applied to the secondary circuit of the motor. If the motor be suppliedwith current at a frequency of 60 cycles, for example, difliculty is encountered, when the voltage at the commutator of the regulating winding or machine exceeds or volts, due to the large commutator and great number of commutator brushes required to transmit the large regulating currents required at these voltages. In accordance with my invention, provision is made for suppressing the field flux in the commutation zone of the regulating winding or machine.

My invention will be better understood from the following description when considered in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Referring to the drawings, Fig. 1 shows a speed control arrangement in which my invention may be embodied; Fig. 2 shows details of construction of the commutator regulating machine; and Fig. 3 shows the invention applied to a two-part commutator regulating apparatus. g

Fig. 1 shows a speed control aggregate or system wherein a regulating machine 1 is provided with a commutator, the brushes 8 of which are interconnected with the secondary circuitiof an induction motor 2 and the slip rings 7 of which are connected through a transformer 3 to a polyphase line 4'. from which current is supplied to the primary circuit of the motor 2.

Assuming the motor 2 and regulating machine 1 to have the same number of poles and to be operated at the same speed, the transformer 3 may be adjusted in a well known manner to vary the voltage applied to the secondary circuit of the .motor by the he quoncy changer or regulating machine 1. As indicated above, the upper limit of the regulating voltage is rather low unless special means are provided for improving the conunutation of the regulating winding or machine. Thus, assuming the rotor winding of the regulating machine to be a multiple winding with oneturn per commutator bar, the voltage per bar, hereinafter designated as e is equal. to

component 1 fflfid representing the part of the total voltage e produced by rotation of the regulating winding or machine and a component due to rotation ofthe field. flux.

If no means are provided for limiting the field flux in the commutating zone of the regulating machine or winding, the total voltage 6, which is equal to e,+e,, is necessarily limited to a value at which good commutation is realized. It is possible, however, to suppress the field in the commutating zone by slotting the stator field structure at points adjacent the commutated conductors of the regulating winding or machine. In this manner, the component "oltage 6 in the comnnitating zone may be suppressed and both the flux 4 and the voltage 6 may be increased in proportion to the quotient obtained by dividing f into f. Thus assumnutator brushes accordoroi the d;

odeoznniutation. Induet 1 coup-let";

LU hare ('liiiQri.

tithea r: Windin' er or Lire :stai'o d bran-hes S in one d!- shiftin the tator 5' and while t3 in the UPPOHIIQ dire 'tion and t through whieh :3 may be eonor: and brushes ot o omte rhreetrou-t non iliuszen wteetzrfh the a, r a nd 'dexerihei he on tved.

g ep 7' info apparent, however that the invention .i suseeptihh) o i hen modified. in nra y \f r to meet the (iii? A .ilinnfi enroi :ed in its we .7 to the r-ieeondar r of said motor. peed control s \s' te;n, a commutator eteetrie machine provided with nail ng eonnerted t": a eoinniutator hai'in sle opposite zones ot id rotor meni- 11., hr 1:. ed relation with said stator mernher hearing:v on said commutator, said tor and brushes being adjustable. and a oaniper winding in the slots of said stator nien'iher.

In witne s whereof, I have hereunto set my hand this 21th day of August; 1927.

HIDDE K. SCI- RAGE 

